Power transistor help

[Gepetto]

Joe,
As others have seen and said, what is the correct way to clean the boards as shown?

Lots of 91%, lots...let it run off the board as you hold it vertically over the trash can while scrubbing with a flux brush (pictured)

 

[wattsabundant]

"Ideal T-strippers " should be a porn site. My I.P.A. alcohol comes in a keg. Currently it's Goose Island. I use 99% alcohol to clean solder flux that is not water soluble.

My suggestion for less aggravation installing outputs is to align the pins on each output to it's future location on the backplanes before installing the backplanes. Lay them out on the bench in 4 columns.

 

[gary33030]

Joe,
Guess I just need to clean, c;ean, clean, etc.
Is there any reason that I cannot use Silicone Hook Up Wire of the correct AWG. I have tons of wire from my drone days!

 

[WOPL Sniffer]

Joe,
Guess I just need to clean, c;ean, clean, etc.
Is there any reason that I cannot use Silicone Hook Up Wire of the correct AWG. I have tons of wire from my drone days!

That wire will not withstand soldering very well and looks like crap. I was with the Army UAV program for 17 years.

 

[Gepetto]

Hi Gary
Yes it is just a matter of clean, clean, clean. If your solvent is dirty from the flux residue washed off, it will dry on the board and redeposit flux residue everywhere. You have to get to the point where your solvent is basically free of residue to restore the original shine of the solder mask.

Like your dishwasher, if the rinse water is dirty, your dishes will come out dirty

On Silicone wire, you can, but like Perry says...

It is great for my soldering pencil wire...

 

[gary33030]

All,

This will be a stupid question. When you clean the flux from the circuit board, do you clean both sides??

 

[George S.]

Yup, usually both sides because the flux laden alcohol gets on both sides and leaves a flux residue as it evaporates and dries. Takes a good amount of work and alcohol to clean boards well.

 

[Gepetto]

All,

This will be a stupid question. When you clean the flux from the circuit board, do you clean both sides??

Yes, the ones coming back to you Gary are cleaned on both sides...shiny

 

[gary33030]

Joe,
Boards arrived this morning. Getting everything ready to work on them this weekend.
Again, Thank you for restoring my backplane boards.
To and family and everyone else: Happy New Year!!!!

 

[gene french]

go gary...go!!!

 

[gary33030]

First Good morning, everyone...
Last night I installed my new repaired backplanes boards. (Thanks again Joe). Installed first roll of transistors, did all the electrical checks and everything passed with flying colors. Installed second roll of transistors. did all the electrical checks but this time also adjusted the Bias voltage. Left channel set to 0.350, right channel set to 0.351. All is good so far. Third row installed. Everything measures good. Installed fourth row. Measured amp again but this time have no Bias voltage.
Voltage off the capacitors: 161.0 volts
No fuses blown including fuses mounted of circuit boards.
I have 15 volts +&- on the control board.
Protection relay closes after about 3 sec. and stays closed unit power down.
0.00 volts on the outputs binding post.
Normal or is something wrong?

 

[WOPL Sniffer]

Take the last row back out and verify that the amp is still within spec, and then I would FIRST, clean the hell out of the control board, and then clean it again. I still see some pretty rough soldering going on there.

 

[gene french]

you could have overtightened the last row...
you only snug them...

 

[WOPL Sniffer]

I would venture to say you MAY have a bad transistor in the last row you added when it failed. Put in the last row one at a time to verify or ohm them out on the bench out of the circuit.

 

[WOPL Sniffer]

Yep, if you are using more than 2 fingers installing the trans/SilPads, you are wanking on them to hard. Inspect the SilPads and mounting area

 

[Vintage 700b]

Very easy to tear a Sil-Pad, how did the DBT respond when you brought it up?
There is a good chance that is where you will find the culprit. Sniff's suggestions to proceed
above are right on. Take it slow, you are getting close. I always check for shorts, (continuity)
before I bring up a row, test each transistor after I install it.

 

[WOPL Sniffer]

check for a solder ball under those 4 sil pads

 

[gary33030]

DBT responded correctely. Bright for about 2 seconds and dims almost completely. Have not had the time yet to pull out the transistors and inspect. Will keep everyone in the loop.

 

[laatsch55]

Have you measured C and E voltage on the bias transistor?

 

[gary33030]

Id assume to test the C and E voltage, the amp is powered up. Red lead on C from meter? Black lead on meter to copper bus? And than the same for E terminal?